1. Field of the Invention
The present invention relates generally to techniques for fingerprinting and identifying Digital Versatile Discs, and more particularly to methods and apparatus for generating multiple content-based IDs or fingerprints and using these fingerprints to uniquely identify a DVD.
2. Description of Related Art
The Digital Versatile Disc (DVD) has become very popular in the past decade thanks to the ubiquitous low-cost DVD players as well as the availability of video content on DVDs. According to DVD Entertainment Group, by the end of 2005, more than 80% of US household will have at least one DVD player. Meanwhile, more than 70,000 DVD titles have been published for Region 1 (US and Canada) since 1997. The increasing number of published DVD titles and the proliferation of digital media jukeboxes and online services demand effective and efficient methods and apparatus for indexing and uniquely identifying a DVD disc.
A digital object can be uniquely identified. Here the term “digital object” is defined as a digital file or bitstream, or a composition of multiple digital files or bitstreams. For example, digital objects can include a computer file stored on a hard disc drive and video bitstreams broadcast or streamed to a TV or computer. A DVD or more precisely the content on a DVD can also be characterized as a digital object comprising multiple files stored on the DVD disc. The structure, format and organization of content on DVDs is described in “DVD Specifications for Read-Only Disc, Part 3: Video Specifications,” Version 1.1, December 1997, published by the DVD Forum. As is known in the art, a digital object can be uniquely identified by passing the object through a hash function that produces a fixed-length output known as hash sum or message digest. A hash sum of a digital object is often called a digital fingerprint because it can be used to uniquely identify the digital object. A popular hash function that is often used to generate digital fingerprint of a digital object is the RFC 1321 specified MD5 hash function. Hereinafter, the term “fingerprint” will be used interchangeably with the term “digital fingerprint.”
While it is useful to fingerprint a DVD by passing all of its data through a hash function such as the MD5 hash function, a fingerprint so generated is often inadequate for advanced identification tasks. For example, a pirated DVD will have a MD5 hash sum that is completely different from that of the original DVD, and the hash sum of the pirated DVD may appear to have no relationship to the hash sum of the original DVD. Similarly, a DVD containing a wide-screen version of a movie may not be easily related to a DVD containing the full-screen version of the same movie because their MD5 hash sums are different. Thus to be able to distinguish a pirated DVD from the original or one version of a movie from another, a more sophisticated method and apparatus for fingerprinting and identifying DVDs is required.